Method of heat management in lpg synthesis from bio-based sources

Abstract

A method is provided for synthesizing bio-based LPG from renewable sources via a bio-based synthetic gas feedstock, including step of recovering heat from an oxygenate conversion zone and forming a heat transfer fluid with increased enthalpy, wherein the heat transfer fluid is used to provide heat for an endothermic reaction zone, and this improves the energy efficiency of the process, reduces or eliminates the need for fired furnaces, and reduces CO 2 emissions from fired furnaces.

1 . A method for producing bio-based LPG, comprising:
 a) reacting a bio-based synthesis gas in an exothermic reaction and forming an LPG-enriched effluent stream, wherein the exothermic reaction generates excess heat;   b) increasing the enthalpy of a heat transfer fluid by absorbing at least a portion of the excess heat with the heat transfer fluid;   c) supplying heat from the heat transfer fluid having increased enthalpy to an endothermic reaction and decreasing the enthalpy of the heat transfer fluid;   d) returning the heat transfer fluid with decreased enthalpy to the exothermic reaction; and   e) recovering the bio-based LPG from the LPG-enriched effluent stream.   
     
     
         2 . The method of  claim 1 , wherein the exothermic reaction is a catalytic oxygenate synthesis reaction to convert the bio-based synthesis gas to bio-based methanol. 
     
     
         3 . The method of  claim 2 , wherein the oxygenates generated by the catalytic oxygenate synthesis reaction comprises at least 50 mol % methanol. 
     
     
         4 . The method of  claim 2 , wherein the exothermic reaction is a catalytic oxygenate conversion reaction to convert the bio-based methanol to the LPG-enriched effluent stream. 
     
     
         5 . The method of  claim 1 , wherein the exothermic reaction is the partial oxidation of bio-methane to form the bio-based synthesis gas. 
     
     
         1 . ethod of claim  1 , wherein the endothermic reaction is stream-methane reforming of bio-based methane to form the bio-based synthesis gas. 
     
     
         7 . The method of  claim 1 , wherein the endothermic reaction is a reverse water gas shift reaction for converting a feedstock comprising CO 2  and H 2  to a gaseous mixture comprising CO and H 2 O over a catalyst having WGS activity at endothermic reaction conditions, wherein the bio-based synthesis gas comprises the gaseous mixture. 
     
     
         8 . The method of  claim 1 , wherein the endothermic reaction is a dehydrogenation reaction, including converting a cycloparaffin to an aromatic and hydrogen, and supplying the hydrogen to the bio-based synthesis gas. 
     
     
         9 . The method of  claim 1 , wherein the exothermic reaction is conducted at a temperature within a range between about 200° C. and about 450° C. 
     
     
         10 . The method of  claim 1  wherein the heat transfer fluid having increased enthalpy is a liquid phase fluid, and the heat transfer fluid having decreased enthalpy is a liquid phase fluid. 
     
     
         11 . The method of  claim 1  wherein the heat transfer fluid having increased enthalpy is a vapor phase fluid, and the heat transfer fluid having decreased enthalpy is a liquid phase fluid. 
     
     
         12 . The method of  claim 2 , wherein the oxygenate synthesis catalyst comprises one or more methanol synthesis-active metals selected from the group consisting of Fe, Cu, Zn, Pt, Ru, Zr, Mo, and Pd. 
     
     
         13 . The method of  claim 2 , wherein the oxygenate synthesis catalyst contains essentially no molecular sieve or zeolitic component. 
     
     
         14 . The method of  claim 4 , wherein the oxygenate conversion catalyst comprises a zeolite having a SiO 2 /Al 2 O 3  molar ratio of less than 90. 
     
     
         15 . The method of  claim 14 , wherein the oxygenate conversion catalyst comprises a small pore molecular sieve selected from Chabazite, SSZ-13, SAPO-34, SSZ-39, MCM-35, EU-12, RHO, SAPO-18, SAPO-56. 
     
     
         16 . The method of  claim 14 , wherein the oxygenate conversion catalyst comprises SSZ-13. 
     
     
         17 . The method of  claim 4 , wherein the oxygenate conversion catalyst contains essentially no water gas shift active metal component, selected from the group consisting of Fe, Cu, Zn, Pt, Ru, Zr, Mo, and Pd. 
     
     
         18 . The method of  claim 1 , wherein the LPG-enhanced gaseous effluent comprises greater than 25 weight % LPG, based on the total hydrocarbon content of the LPG-enhanced effluent. 
     
     
         19 . The method of  claim 1 , wherein the LPG-enhanced gaseous effluent comprises less than 25 weight % C5+ hydrocarbons, based on the total hydrocarbon content of the LPG-enhanced gaseous effluent stream. 
     
     
         20 . A method for producing bio-based LPG, comprising:
 a) contacting a biogas comprising biomethane with an oxidizing gas selected from O 2 , CO 2  and H 2 O or combinations thereof at reforming reaction conditions in a reforming reaction zone to form a fresh bio-based synthesis gas;   b) blending at least a portion of the fresh bio-based synthesis gas with a synthesis gas recycle stream to form a blended bio-based synthesis gas;   c) reacting the blended bio-based synthesis gas in an oxygenate synthesis zone containing an oxygenate synthesis catalyst and forming a gaseous synthesis reaction product comprising oxygenates, wherein the oxygenates include at least 50 mol % methanol;   d) reacting the gaseous synthesis reaction product in an oxygenate conversion zone containing oxygenate conversion catalyst and forming the LPG-enriched effluent stream;   e) increasing the enthalpy of a heat transfer fluid by absorbing at least a portion of the excess heat generated in the exothermic oxygenate conversion reaction with the heat transfer fluid;   f) supplying heat from the heat transfer fluid having increased enthalpy to an endothermic reaction and decreasing the enthalpy of the heat transfer fluid; and   g) recovering the bio-based LPG and the synthesis gas recycle stream from the LPG-enriched effluent stream.   
     
     
         21 . The method of  claim 20 , wherein the endothermic reaction is stream-methane reforming of bio-based methane to form the bio-based synthesis gas. 
     
     
         22 . The method of  claim 20 , wherein the endothermic reaction is a reverse water gas shift reaction for converting a feedstock comprising CO 2  and H 2  to a gaseous mixture comprising CO and H 2 O over a catalyst having WGS activity at endothermic reaction conditions, wherein the bio-based synthesis gas comprises the gaseous mixture. 
     
     
         23 . The method of  claim 20 , wherein the endothermic reaction is a dehydrogenation reaction, including converting a cycloparaffin to an aromatic and hydrogen, and supplying the hydrogen to the bio-based synthesis gas. 
     
     
         24 . The method of  claim 20 , wherein the oxygenate conversion reaction is conducted at a temperature within a range between about 200° C. and about 450° C. 
     
     
         25 . The method of  claim 20 , wherein the heat transfer fluid having increased enthalpy is a liquid phase fluid, and the heat transfer fluid having decreased enthalpy is a liquid phase fluid. 
     
     
         26 . The method of  claim 20 , wherein the heat transfer fluid having increased enthalpy is a vapor phase fluid, and the heat transfer fluid having decreased enthalpy is a liquid phase fluid. 
     
     
         27 . The method of  claim 20 , wherein the oxygenate synthesis catalyst comprises one or more methanol synthesis-active metals selected from the group consisting of Fe, Cu, Zn, Pt, Ru, Ce, Al, Si, Zr, Ti, Mo, P, and Pd. 
     
     
         28 . The method of  claim 20 , wherein the oxygenate synthesis catalyst contains essentially no molecular sieve or zeolitic component. 
     
     
         29 . The method of  claim 20 , wherein the oxygenate conversion catalyst comprises a zeolite having a SiO 2 /Al 2 O 3  molar ratio of less than 90. 
     
     
         30 . The method of  claim 29 , wherein the oxygenate conversion catalyst comprises a small pore molecular sieve selected from Chabazite, SSZ-13, SAPO-34, SSZ-39, MCM-35, EU-12, RHO, SAPO-18, SAPO-56. 
     
     
         31 . The method of  claim 29 , wherein the oxygenate conversion catalyst comprises SSZ-13. 
     
     
         32 . The method of  claim 20 , wherein the oxygenate conversion catalyst contains essentially no water gas shift active metal component, selected from the group consisting of Fe, Cu, Zn, Pt, Ru, Zr, Mo, and Pd. 
     
     
         33 . The method of  claim 20 , wherein the LPG-enhanced gaseous effluent comprises greater than 25 weight % LPG, based on the total hydrocarbon content of the LPG-enhanced effluent. 
     
     
         34 . The method of  claim 20 , wherein the LPG-enhanced gaseous effluent comprises less than 25 weight % C5+ hydrocarbons, based on the total hydrocarbon content of the LPG-enhanced gaseous effluent stream.